This invention relates to a fluid flow control device that combines the functions of pressure regulation and selectable flow control. That is, the device regulates the pressure at the outlet to a predetermined value and it responds to a suitable control signal to permit or prevent fluid flow. The device will be referred to herein as a regulator valve. The device is particularly suitable for use in irrigation applications, although it is not limited to this use.
Agricultural irrigation systems typically have a main pipeline and multiple secondary and tertiary distribution lines branching therefrom. Water (with or without added fertilizer, herbicide, insecticide etc.) is supplied to the end of the pipeline. Sprinkler heads, branch laterals, or other distribution means are mounted at intervals along the length of the pipeline for distributing the water. The sprinkler heads or other distribution means can be mounted more or less directly to the main pipeline or at some point along the length of branch distribution laterals that supply the water application devices for growing the crops. In either case the flow rate of water through a sprinkler head or other application device is dependent on the hydraulic pressure at the inlet of the device. That pressure can vary along the length of the pipeline due to friction losses in the pipe and undulations in the local terrain. When it is critical to control the flow rate through an application device a pressure regulator is placed between the pipeline and the device to assure a known hydraulic pressure at the device's inlet, regardless of its location along the length of the distribution system or undulations in the local terrain. A typical pressure regulator of this type is shown in U.S. Pat. No. 4,543,985.
In some applications it may be also desirable to be able to turn the flow of individual application devices on or off, in addition to controlling the pressure seen by the inlet of the device. Examples where this would be advantageous include a center pivot machine having a swing span pivotably connected to the moving end of the pipeline. The swing span swings into the corners of a field to irrigate portions that would otherwise be missed by the circular pattern covered by the main pipeline. The swing span folds in when the main pipeline is opposite an edge of the field and swings out into a corner. U.S. Pat. Nos. 4,011,990 and 5,695,129 describe such a machine. The main pipeline may stop while the swing span irrigates the corner portion. In that case, it would be desirable to turn off the main pipeline sprinklers. The swing span sprinklers need to be off when the swing span is not irrigating a corner. Another example where on-off control is desirable is where field conditions are known to vary from one location to another and the irrigation machine is programmed to apply water and/or chemicals at differing rates dependent on these known field conditions. A third example of where on-off control is desirable is in an orchard, vineyard, golf course, or other application, where it is desirable to turn on or off only a portion of the distribution devices or branch distribution laterals that supply the water application devices connected to a supply system.
My prior combined pressure regulator and shut-off valve, which is shown and described in U.S. Pat. No. 6,374,853, incorporates a selectable on-off feature. This prior valve of mine utilizes first and second tubular plungers each connected to first and second flexible diaphragms, respectively. This valve is particularly well suited to installation in the tubular drop that connects a sprinkler head to a main or branch pipeline wherein the valve functions as a normally open valve.